type EchoServer impl(echo::#Service) {
    verbose: Bool
};

method EchoServer.echo: rpc::Method[echo::#Request, echo::#Response]
    &(this) => &(req) =>
        if this.verbose:
            { return { |echo::#Response| {
                content: { "Reply: ?" req.content }
            } } },
        else:
            { return { |echo::#Response| {
                content: req.content
            } } };
entry
    { rpc::serve {
        service: echo::#Service,
        backend: echo::DefaultServerBackend,
        options: {},
        constructor: &(arg,_) =>
            { return { |echo::#Service| { |EchoServer| {
                verbose: arg.verbose
            } } } }
    } }
    . { crash-on-error };
